It is a measure of the political decibels generated by the mayor of London that conference organisers followed his turn on the stage in Birmingham yesterday with a brass ensemble. Even so, it was not enough to drown out his challenge to the government to consider tightening the law on strike ballots, after yesterday's day of tube disruption in London. On Sunday delegates arriving in Birmingham were confronted with thousands of anti-cuts protesters, and at Labour's conference last week David Miliband's defeat was attributed by some observers to a reluctance to commit himself to join a day of action. Industrial relations are back on the political agenda.

The mayor's idea of requiring a 50% turnout in strike ballots should be seen in the context of the tube strike over the loss of ticket office staff overlaid with a certain amount of conference-inspired political grandstanding. His proposal could result in outcomes almost as undemocratic as the election of Mr Johnson himself, who won London with the support of less than a quarter of the capital's voters. But aside from fractious confrontations between the mayor and rail workers, the trade unions are facing their most difficult and most important choices since the Thatcher era.

Cuts in public spending are going to cost thousands of jobs. They will mean tough deals for workers who are already among the lowest-paid in Britain. Last month all of Birmingham's 26,000 non-schools staff were warned of changes in their contracts, while Suffolk council is planning to outsource all council work. That will mean fewer jobs, and those left will be less well-paid. The unions know how reluctant their members are to strike at a time of such insecurity. Last year only 750,000 days were lost, and those were almost entirely in the public sector. When it comes to opposing the cuts, it is already clear that where there are strikes, they are more likely to be local than national, although there will be a rally on the day of the comprehensive spending review and a day of action in March.

Public sector disputes always risk hitting the most vulnerable and alienating public support. There is a painful but unavoidable trade-off between accepting worse pay and conditions (particularly pensions) and protecting jobs. So trade unionists are increasingly thinking less of all-out industrial action and more of a kind of asymmetrical campaign fought at local level, an alliance between the people who rely on public services as well as those who supply them. Most importantly the particular – the loss of jobs and services – has to be linked to the general: the case for a steadier, slower reduction of the deficit. The government has had an easy ride over the summer. Now it must be challenged.